Please help me with the question below. Really appreciate it if you can solve these with a proper explanation. So that I can understand how to do them. Thank you.

Please note P[X_i=1] = 4/10;

2. Let Xi = 1 denote Heads and X; = 0 Tails in the ith toss. Consider 3 independent tosses X1, X2, X3 of a biased coin with the probability of a Head given by P(X, = 1) = 4/10; Calculate (fully justify your computations): (a) P(X1 + X2 + X3 = 2) (b) P(X1 + X2 + X3 = 2|X1 = 1) (c) P(X1 + X2 = 2 X3 = 0) (d) P(X1 + X2 = 2 X3 = 1)