(a) It is the duty of the representative to invest the ward’s money. A representative is chargeable with interest at a rate equal to the rate on 90-day United States Treasury Bills upon any money that the representative wrongfully or negligently allows to remain uninvested after it might have been invested. Reasonable sums of money retained uninvested by the representative in order to pay for the current or imminent expenses of the ward shall not be considered wrongfully or negligently uninvested.
     (b) Upon receiving the approval of the court, a representative may hold any investments, or any increase thereof, received by the representative at the time of the representative’s appointment or acquired by the ward, although the investment is not otherwise authorized under this Act, and the court has power to direct the representative in connection therewith.
     (c) A representative may invest only in the types of property specified in Sections 21-2.01 through 21-2.15.