(a) Germaneness. No funds in excess of the contract price may be obligated or expended unless the additional work to be performed or materials to be furnished is germane to the original contract. Even if germane to the original contract, no additional expenditures or obligations may, in their total combined amounts, be in excess of the percentages of the original contract amount set forth in subsection (b) unless they have received the prior written approval of the construction agency. In the event that the total of the combined additional expenditures or obligations exceeds the percentages of the original contract amount set forth in subsection (b), the construction agency shall investigate all the additional expenditures or obligations in excess of the original contract amount and shall in writing approve or disapprove subsequent expenditures or obligations and state in detail the reasons for the approval or disapproval.
     (b) Written determination required. When the contract amount is no more than $75,000, the percentage shall be 9% (maximum $6,750). When the contract amount is between $75,001 and $200,000, the percentage shall be 7% of the amount above $75,000 plus $6,750, but not to exceed 7% of $200,000 (maximum $14,000). When the contract amount is between $200,001 and $500,000, the percentage shall be 5% of the amount above $200,000 plus $14,000, but not to exceed 5% of $500,000 (maximum $25,000). When the contract amount is in excess of $500,000, the percentage shall be 3% of the amount above $500,000 plus $25,000.