When I first saw the question, I thought it is a long question, but the important information is just N(t)=150-10t

I need it to solve the problem,

b)Determine the value of N(-5).   Just put -5 into the  N(t)=150-10t, and then get the answer 150-10*(-5)=200

c)write in words the meaning of N(-5). The way to solve this problem is just understand the meaning of the question and N(t)=150-10t. N stands for number of cups of hot chocolates sold , and t stands for temperature, so the answer of this problem is 200 cups of chocolates were sold when the average temperature is -5.

d)What was the average temperature if 190 cups of hot chocolate were sold? this question is similar as b) just put 190 into N(t)=150-10t, and then the answer is -4.