Corollary to the doctrine of exhaustion of administrative remedies is the doctrine of primary jurisdiction; that is, courts cannot or will not determine a controversy involving a question which is within the jurisdiction of the administrative tribunal prior to the resolution of that question by the administrative tribunal, where the question demands the exercise of sound administrative discretion requiring the special knowledge, experience and services of the administrative tribunal to determine technical and intricate matters of fact. 53 [53]   Nonetheless, the doctrine of exhaustion of administrative remedies and the corollary doctrine of primary jurisdiction, which are based on sound public policy and practical considerations, are not inflexible rules. There are many accepted exceptions, such as: (a) where there is estoppel on the part of the party invoking the doctrine; (b) where the challenged administrative act is patently illegal, amounting to lack of jurisdiction; (c) where there is unreasonable delay or official inaction that will irretrievably prejudice the complainant; (d) where the amount involved is relatively small so as to make the rule impractical and oppressive; (e) where the question involved is purely legal and will ultimately have to be decided by the courts of justice;54[54] (f) where judicial intervention is urgent; (g) when its application may cause great and irreparable damage; (h) where the controverted acts violate due process; (i) when the issue of non-exhaustion of administrative remedies has been rendered moot;55[55] (j) when there is no other plain, speedy and adequate remedy; (k) when strong public interest is involved; and, (l) in quo warranto proceedings. x x x56[56]   WHEREFORE, the petition is GRANTED. Consequently, the Decisions dated January 6, 2005 and April 20, 2005, and the Resolutions dated March 10, 2005 and June 29, 2005 of the Court of Appeals, nullifying and setting aside the Writ of Preliminary Injunction issued by the Regional Trial Court (RTC), Branch 52[52] ACWS, Ltd. v. Dumlao, supra, at 802. 53[53] Paloma v. Mora, G.R. No. 157783, September 23, 2005, 470 SCRA 711, 725; Fabia v. Court of Appeals, 437 Phil. 389, 403 (2002). 54[54] Rocamora v. Regional Trial Court-Cebu (Branch VIII), No. L-65037, November 23, 1988, 167 SCRA 615, 623. 55[55] Carale v. Abarintos, 336 Phil. 126, 137 (1997). 56[56] Castro v. Sec. Gloria, 415 Phil. 645, 651-652 (2001).