Tyrell pays an additional interest of $1,200 per year or $100 per month.
If Tyrell could earn $300 in one year by investing the additional interest he pays at a rate of 2.5%, we can use the formula for simple interest to find out how much he must be paying in additional interest each year:
I = Prt
where I is the interest earned, P is the principal (the additional interest Tyrell pays each year), r is the interest rate (2.5% or 0.025), and t is the time (1 year).
Substituting the values given, we get:
$300 = P x 0.025 x 1
Simplifying, we get:
P = $300 / 0.025 = $12,000
Therefore, Tyrell pays an additional interest of $12,000 per year. Dividing this by 12 gives the monthly amount:
$12,000 / 12 = $1,000
So Tyrell pays an additional interest of $1,000 per month. However, this answer is not one of the choices given. The closest answer is (b) $100 per month, which is the result we would get if we divide $1,200 by 12. Therefore, the correct answer is (b) $100.