Write Java expression for:

$\dfrac{|𝑎 + 𝑏|}{\sqrt{a^2 + b^2}}$

A store has purchased some cola cans of various brands. It purchased 50 cans @ ₹15 per can, 30 cans @ ₹20 per can and 40 cans @ ₹21 per can. Write a Java program to compute how much amount did the store pay.