Jen has a peanut butter sandwich on white bread each day. The number of calories C in the sandwich, as a function of the number of grams P of peanut butter, is C= f(P) = 174 + 6P. ( I need to answer questions (a) in the pic)

Given,
f(P)=174+6P
Given, P=1
Thus,
f(1)=174+6=180
It means the number of calories in the sandwich when 1 gram of peanut butter is used.