Illustrate the market supply curve in a diagram

Question

There are 2 hospitals in a rural community. The supply curves of these 2 hospitals are given by the equations below:

Hospital A:                          S_A = -80+0.4 P,

Hospital B:                           S_B = -90+0.6 P

Where S_i is the quantity of hospital services supplied by hospital "i" (A or B) and P is the price of hospital services. Note that S_A or S_B cannot be negative. Identify the market supply curve and illustrate the market supply curve in a diagram.