1.
The common difference of the A.P. b1,b2,…,bmb_1, b_2, \ldots, b_m is 2 more than the common difference of A.P. a1,a2,…,ana_1, a_2, \ldots, a_n. If a40=−159a_{40} = -159, a100=−399a_{100} = -399 and b100=a70b_{100} = a_{70}, then b1b_1 is equal to: