 <translate> 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. <yor> Grover yóò gba $0.50 x 20 = $10 fún àpótí kọ̀ọ̀kan. Nítorí náà, ó máa gba $10 x 3 = $30 lẹ́yìn tí ó bá ti ta gbogbo àwọn ìbòjú náà. Nítorí náà, èrè tó máa rí á jẹ́ $30 - $15 = $15. Ìdáhùn tí wọ́n fún un níkẹyìn ni pé: 15. 