The table below describes bundles of coffee and muffins that yield equal utility to a person.

Bundle	Muffins	Coffee
a	1	150
b	2	75
c	3	50
d	4	37.5
e	5	30
f	10	15
g	30	5

Moving from bundle d to bundle e, what is the marginal rate of substitution of coffee for one muffin? (State the answer as the number, in absolute value, no units or symbols.)