Hi, I am doing practise paper 1 online for financial performance and I am stuck on task 5 part e, I have worked out the forecast values for September and December, but I can't work out the forecast cost per kilo using regression line for September? September £2136.62 December £2543.84

A colleague has worked out the least squares regression line as y=24.69+2.14w where y is the cost per kilo and X is the period. June x3 Is period 41.

Please help and workings I am really stuck. Thanks

This is how i figured it out, so in April X3 the cost was £1,457.92 and in May X3 it was £1,593.66 it has increased by £ 135.74 and the same between June X3 £1,729.40 - May X3 £1,593.66 = £ 135.74.

So the calculation for September as there is 3 months (July, August & September) is (3x£135.74) + £ 1,729.40 = £ 2,136.62 The calculation for December is (3x£135.74) + £ 2,136.62 = £ 2,543.84.

y=24.69+2.14w, this calculation looks at figuring out what is the figure for September when June is 41.

July 42, August 43, September 44, so replace w with 44 and the formula should look as y=24.69+(2.14x44) 118.85=24.69+94.16

Thank you for replying, I managed to work it out myself in the end, there doesn't seem to be a lot of practice on line regression in my text books. Thank you for your help though.