A business executive has the option to invest money in three plans: Plan A guarantees that each $ invested will earn $0.50 a year later; plan B guarantees that each $ invested will earn $1.50 after 2 years. In plan C, $1 invested in year 1 and $1 invested in year 2 will return $0.70 in the third year and $3.00 in the fourth year. In plan A, investments can be made annually (t=1, 2, 3, ...), and in plan B, investments are allowed for periods that are multiples of two years only (t=2, 4, 6, ...). How should the executive invest his $100.000 to maximize the earnings at the beginning of year 4