=5 × (-4 + 5 i) + 3 i×(-4 + 5 i)→→Used the identity, (a+b)×(c+d)=a×(c+d)+b×(c+d), Also Used distributive property of multiplication over addition and subtraction.
It is related to econometrics, however using simple algebraic logic we can solve this problem. General formula with residual is , where r is a residual. Plugging the pair into the formula, we obtain that and r=0.5
, where r is a residual. Plugging the pair into the formula, we obtain that 
and r=0.5