Verify the first special case of the chain rule for the composition f∘c in each of the cases:

(a) f(x, y)=xy, c(t)=(et, cost)

(b) f(x, y)=exy, c(t)=(3t2,t3)

(c) f(x, y)=(x2+y2)log√x2+y2,c(t)=(et, e−t)

(d) f(x, y)=xexp(x2+y2),c(t)=(t,−t)

Luke started a weight-loss program. the first week, he lost x pounds. the second week, he lost pounds less than times the pounds he lost the first week. the third week, he lost 1 pound more than of the pounds he lost the first week. liam started a weight-loss program when luke did. the first week, he lost 1 pound less than times the pounds luke lost the first week. the second week, he lost 4 pounds less than times the pounds luke lost the first week. the third week, he lost pound more than times the pounds luke lost the first week.