(1) Of Sheila’s show dogs, exactly 3 have won prizes of at least $500.
Total = Dogs who won prize money equal to and greater than $500 + Dogs who won Prize money less than $500
But we don't have information exactly how many didn't won any prize money or prize money less than 500$
(Insufficient)

(2) Of Sheila’s show dogs, exactly 40% have not won a prize of $500 or more.
40% haven't won a prize equal to or greater than $500
But (40% of what no.?)
No exact no. Is given to determine the total no. Of Dogs.
(Insufficient)

Combining both:
60% who won prize money equal to or greater than 500$ = 3
So 40% who didn't won that much prize money = 2
Total no. Of dogs = 5
(Sufficient)

Answer is C

Posted from my mobile device