The cost of 2 bags of maize and 3 bags of beans is Ksh 12,500. The cost of 3 bags of maize and 5 bags of beans is Ksh 20,000. Find the cost of one bag of each item. (3 marks)

Let $m$ be the cost of one bag of maize and $b$ be the cost of one bag of beans.
From the given information:

Multiply equation (1) by 3 and equation (2) by 2 to eliminate $m$:

The cost of one bag of maize is $\boxed{\text{Ksh. } 2,500}$ and the cost of one bag of beans is $\boxed{\text{Ksh. } 2,500}$.

13. Given the column vectors: $a = \begin{pmatrix} 2 \\ -3 \end{pmatrix}$, $b = \begin{pmatrix} 5 \\ 1 \end{pmatrix}$, $c = \begin{pmatrix} -4 \\ 6 \end{pmatrix}$. Find $|3a + b - c|$.

14. A Kenyan bank buys and sells foreign currency as follows:

Since the tourist is changing foreign currency to Kenya Shillings, the bank is buying the foreign currency from the tourist. Therefore, we use the "Buying (Ksh)" rates.