Problem Solving (PS) | An item, when sold at a certain price, yields r% profit. Had it been s

An item, when sold at a certain price, yields r% profit. Had it been sold for $s more, the profit percentage would have been t%. What is its cost price?

A. 100r/(t-s)
B. 100s/(t-r)
C. s/100(t-r)
D. st/100(t-r)
E. (t-r)/100s

---