To avoid having a voidable contract, all 'time is of the essence' deadlines set by the contract must be met: a. within 24 hours of the stated deadline.
b. within 48 hours of the stated deadline.

None of the choices are needed

Explanation:

As we know that

The contract is an agreement between two parties who are eligible and enforceable by  law

The voidable contract is an agreement that is not unenforceable by law due to various reasons like - party failure to complete the contract on time, fraud, misrepresentation, etc

So in the case of the voidable contract, no grace period is applicable neither 24 hours nor 48 hours as if there is a deadline so the same should be considered