Payprice Supermarket held a sale at the "Fresh Food Corner". Ms Ng, Mdm Lim, Mr Yeo and Mrs Heng were at Payprice for this sale. As the items were not pre-packed, customers were charged by the weight of the seafood they have selected. The weight of their seafood purchase was summarized in the following table.

	Ms Ng	Mdm Lim	Mr Yeo	Mrs Heng
Cuttlefish (kg)	0.75	0.60	1.30	1.10
Japanese Sea Bass (kg)	1.20	1.45	0.90	1.80
Tiger Prawns (kg)	0.20	0.45	0.50	0.30

Ms Ng, Mdm Lim and Mr Yeo paid $28.51, $35.79 and $33.40 respectively for their purchase. Mrs Heng found that she only had $50 with her. Determine whether she has enough money to pay for her purchase.

1. Formulate a system of linear equations based on the purchase records.

Let $x$, $y$, and $z$ be the price per kg of Cuttlefish, Japanese Sea Bass, and Tiger Prawns respectively.

From the table, we set up the following equations based on the amounts paid:

2. Solve the system of equations using a graphing calculator.

Using a graphing calculator to solve the system, we obtain:
$x = 7.8$
$y = 15.9$
$z = 17.9$

The unit prices are $\char36{}7.80/\text{kg}$ for Cuttlefish, $\char36{}15.90/\text{kg}$ for Japanese Sea Bass, and $\char36{}17.90/\text{kg}$ for Tiger Prawns.

3. Calculate the total cost of Mrs Heng's purchase.

Total cost for Mrs Heng $= 1.10x + 1.80y + 0.30z$
$= 1.10(7.80) + 1.80(15.90) + 0.30(17.90)$
$= 8.58 + 28.62 + 5.37$
$= 42.57$

4. Compare the cost to the amount of money Mrs Heng has to draw a conclusion.

Mrs Heng has $\char36{}50$.
Since $\char36{}42.57 \le \char36{}50$, she has enough money to pay for her purchase.