Lucy, Jane, Risa and Anna jointly contributed to the cost of a present for their schoolmate. Lucy's contribution is ⁷₈ of the total contribution made by the four girls. The ratio of Anna's contribution to the total of Jane's and Risa's contribution is 3 : 2. What is the total contribution by the four girls if Jane's contribution is ¹₈ of Risa's contribution and the total amount contributed by Lucy and Anna is $3762?

Lucy	Jane	Risa	Anna	Total
7x45	1x45			8x45
	2x9		3x9
	1x2	8x2
315 u	2 u	16 u	27 u	360 u

Working backwards.

Total amount that Jane and Risa had is the combined repeated identity.
LCM of 2 and 9 = 18

Total amount that Jane, Risa and Anna had is the next combined repeated identity.
LCM of 1 and 45 = 45 

Total amount contributed by Lucy and Anna
= 315 u + 27 u
= 342 u

342 u = 3762

2 u = 3762 ÷ 342 = $11

Total contribution by the four girls
= 360 u
= 360 x 11
= $3960

Answer(s): $3960