Except as otherwise provided in this part and Title 28, chapter 2, parts 16 and 17, the specific performance of an obligation may be compelled when:
(1) the act to be done is in the performance, wholly or partly, of an express trust;
(2) the act to be done is such that pecuniary compensation for its nonperformance would not afford adequate relief;
(3) it would be extremely difficult to ascertain the actual damage caused by the nonperformance of the act to be done; or
(4) it has been expressly agreed in writing, between the parties to the contract, that specific performance thereof may be required by either party or that damages shall not be considered adequate relief.