RT plc sells three products.
Product R has a contribution to sales ratio of 30%.
Product S has a contribution to sales ratio of 20%.
Product T has a contribution to sales ratio of 25%.
Monthly fixed costs are £100,000. If the products are sold in the ratio:
R: 2 S: 5 T: 3
The monthly break-even sales revenue, to the nearest £1, is:

(a) £400,000

(b) £411,107

(c) £425,532

(d) impossible to calculate without further information.