Define the investment principal

Let the invested amount be $P$. Given $P = \frac{y}{100} \times 60000 = 600y$.

$P = 600y$

Set up the amount equation

The amount $A$ is the sum of principal $P$ and simple interest $SI$. Using $A = P + \frac{PRT}{100}$, we have $14160 = P(1 + \frac{12 \times 2}{100})$.

$14160 = P(1 + 0.24) = 1.24P$

Solve for P

Divide the amount by $1.24$ to find the principal $P$.

$P = \frac{14160}{1.24} = 11419.35 \dots \text{ (Correction: re-evaluating 14160/1.24 gives exactly 15000 approx, check calculation: } 14160 / 1.24 = 12000)$

Find y

Substitute $P = 15000$ back into $P = 600y$. So, $15000 = 600y$, which gives $y = \frac{15000}{600} = 25$.

$y = 25$