In what direction must the current I2 flow in the straight wire in order to create a field at the center of the loop in the direction opposite to that created by the loop?

Right to left

Explanation:

From right hand thumb rule, the magnetic field at the centre of loop points out of the plane of paper. Thus the straight wire current should create magnetic field into the plane of paper at the centre. Hence the direction of current in long wire should be from right to left

b.

explanation:

ice to water 1 water to vapour 2 latent heat