The answers are for
a. is between 21 and 27 C
b. when the temperature reaches 21 there is enough temperature to work as a catalyst for the photosynthesis reaction to go on with full capacity .. when increasing the temperature to 27 C it wont do the reaction any bad as it is still within good fair positive limits that can be tolerated by the organism and manipulated for its favor yet it wont that increase in temp I mean do any good for the photosynthesis is already at optimum under the temp effect
c. I suggest 21 C for at this degree photosynthesis is at its optimal state yet it is less costly than increasing the temperature any more within the positive range
