 
 <translate> Work done by the waste pipe in 1 minute = 1/15 - (1/20 + 1/24) = - 1/40
Volume of 1/40 part = 3 gallons\
Volume of whole = 3 * 40 = 120 gallons. So the final answer is (C). <ibo> Ọrụ nke ọkpọkọ mkpofu na 1 nkeji = 1/15 - (1/20 + 1/24) = - 1/40 Mpịakọta nke 1/40 akụkụ = 3 galọn\ Mpịakọta nke dum = 3 * 40 = 120 galọn. Ya mere, azịza ikpeazụ bụ (C). 