Let the first term be a and the common difference be d and n be the nth term
t1 is the first term, so a=4
tn = a + (n-1)d
2 = 4 + (4-1)d
or 3d = 2-4
or d = -2/3
So, t8 = 4 + (8-1)(-2/3)
or t8 = 4+7*2/3 = -2/3
Sn = n/2[2a + (n − 1) * d]
S5 = 5/2[2*4 + (5-1) * -2/3] = 40/3