 
<translate> Grover zai sami $0.50 x 20 = $10 ga kowane akwati. Don haka, zai samu $10 x 3 = $30 bayan ya sayar da duk abin rufe fuska. Saboda haka, yawan ribarsa zai zama $30 - $15 = $15. Amsar ƙarshe ita ce: 15. <eng> Grover will earn $0.50 x 20 = $10 for each box. So, he will earn $10 x 3 = $30 after selling all the face masks. Therefore, his total profit will be $30 - $15 = $15.
The final answer: 15. 