Could you please tell me what's wrong with my solution?

The question is:

Consider a competitive market where market demand is given by:

Qd = 54 - P/2

where Qd is the quantity demanded and P is the price.

Assume that the market supply curve is given by the following:

Qs = P - 3

What is the value of the producer surplus in the competitive market equilibrium?

Draw the market diagram to check whether your answer makes sense. Work with 2 decimals in your calculation (e.g., for P* and Q*). If your answer involves more than 2 decimal places, please round your answer to 2 decimal places (e.g., 24.03).

Below is my working:

Qd=Qs at equilibrium

So 54-p/2 = p-3

p+2/p=54+3

3p/2=57, p=38

when p=38, q=38-3=35.

If I draw it on a graph, for PS, trapezium is made, and using the formula for trapezium:

(3+38)*35*0.5=717.5

But this answer is wrong, could you tell me what's wrong with my solution in detail?