Rule of 78, for a 12-month period, the last term in the sequence is 12 and the series sums to 78. for an 14 month period, the last term is and the series sum is . for a 16 month period, the last term is and the series sum is . for a 20 month period, the last term is and the series sum is .

1. For a 14 month period the last term in the sequence is 14 and the series sum is;
1+2+3+4+5+6+7+8+9+10+11+12+13+14
= 105

2. For a 16 month period, the last term in the sequence is 16 and the series sum is
1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16
= 136

3. For a 16 month period, the last term of the sequence is 20 and the series sum is;
1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20
=210

21, i'm pretty sure it's right lol

Answer: d. 48 step-by-step explanation: i used a calculator so i am 100% sure these are right   mark as brainliest?