Short-Run Supply In a short-run the number of firms in the industry is, temporarily, fixed Let n be the number of firms 1=1, S (p)is firm i's supply function The industry's short-run supply function is S(p)=∑S;(p) i=1Short-Run Supply In a short-run the number of firms in the industry is, temporarily, fixed. Let n be the number of firms; i = 1, … ,n. Si (p) is firm i’s supply function. The industry’s short-run supply function is S p Si p i n ( ) =  ( ). =1