125 vaci .................78cai................2592 kg fan
109 vaci..................78cai.................2400kg fan
16vaci.................................................192 kg ⇒ 1 vaca consuma 12kg fan
125 vaci consuma 125·12 = 1500kg ⇒ 78cai consuma 2592 - 1500 = 1092kg
⇒ 1 cal consuma 1092: 78 = 14kg fan