Section 408.020 allows creditors to recover interest at a rate of nine percent “when no other rate is agreed upon, for all moneys after they become due and payable, on written contracts, and on accounts after they become due and demand of payment is made.” Section 408.020. Parties may also agree on a specific rate of interest which will control if it is not otherwise excessive under the law. Schnucks Carrollton Corp. v. Bridgeton Health and Fitness Inc., 884 S.W.2d 733, 740 (Mo.App. E.D.1994). If no other rate of interest is agreed upon, the rate in Section 408.020 is applicable. Id. Prejudgment interest may only be awarded where the claim is liquidated. Miller v. Gammon & Sons, Inc., 67 S.W.3d 613, 624 (Mo.App. W.D.2001). To be liquidated, the claim must be fixed and determined or readily ascertainable by computation or a recognized standard. Id. The award of prejudgment interest in a case in which damages are liquidated is not a matter of court discretion; it is compelled. Comens v. SSM St. Charles Clinic Medical Group, Inc., 335 S.W.3d 76, 82 (Mo.App. E.D.2011); Holtmeier v. Dayani, 862 S.W.2d 391, 407 (Mo.App. E.D.1993). The purpose of statutory prejudgment interest is to promote settlement of lawsuits and fully compensate plaintiffs by accounting for the time-value of money. Comens, 335 S.W.3d at 80. In an action for breach of a written contract, interest ordinarily runs from the date of the breach or the time when payment was due under the contract. Miller, 67 S.W.3d at 624-25.