Explanation

(c) Efficiency of transformer,
$\eta = \frac{Output\ power}{Input\ power}$
$\Rightarrow \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \frac{88}{100} = \frac{880}{P_{i}}$
$\Rightarrow \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ P_{i} = 1000\ W$
Input current , $\ \ \ \ \ \ \ \ \ \ \ I_{p} = \frac{P_{i}}{V_{i}}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = \frac{1000}{2200} = 0.45\ A$