The price of gas at Mike’s gas station is $1.50per litre. If a customer buys a minimum of10 litres, a discount of $5 is applied.This can be modelled by the following function, L, which gives the total cost when buyinga minimum of 10 litres at Mike’s gas station.L(x)=1.50x-5,x≥10where x is the number of litres of gas that a customer buys.

$70=1.50x-5$ (M1)

$\left(x=\right)50$litres A1

[2 marks]

$1.30x$ (A1)

$1.30x<1.50x-5$ (M1)

Note: Award M1 for a graph showing two intersecting linear functions, provided one function has a $y$-intercept of $0$ and the other function has a negative $y$-intercept.

(minimum value of$k=$) $25$ A1

Note: Accept $x>25$.

[3 marks]

$L\left(40\right)=1.50\times 40-5$ (M1)

$=\$55$ A1

[2 marks]