Assume that the riskfree rate increases but the market risk

Assume that the risk-free rate increases, but the market risk premium remains constant. What impact would this have on the cost of debt?

the answer is : it will increase and the reason is as below

Cost of debt C is given by formula = RFRate+IP + DRP + LP + MRP

RFRate = Real risk-free rate.

IP = Inflation premium.

DRP = Default risk premium.

LP = Liquidity premium.

MRP = Maturity risk premium.

now in equation above

Cost of debt is directly proportional to RFrate assuming premium rate is constant

hence it increases.