The employer contribution does not get deducted from her paycheck. To find the amount deducted from her check we take 4% of 1305.60 = 0.04(1305.60) = $52.22.
If the population quadruples every period say hour, that means the "rate of growth" is 300%, so whatever the current amount, increased by 3 times as much is 4 times the current amount, or a quadrupled amount.