Meat prices: use the printed table consistently

Four housewives bought three different types of meat from the same meat seller. The mass of meat and the total each housewife paid are shown in the table below.

	Mrs Lee	Mrs Nasri	Mrs Vicnesh	Mrs Parker
Chicken (kg)	0.3	0.5	0.6	0.8
Mutton (kg)	0.4	0	0.5	$a$
Duck (kg)	0.6	0.4	0	1
Total amount ($)	10.7	6.5	7	18

Find the value of $a$.4 marks