In this article, an inventory model is developed under the situation in which a credit period is offered by the supplier to the purchaser. It is assumed that deterioration rate is a function of time and demand rate in the power law form of the price is considered. Shortages are allowed and are partially backordered with an exponentially decreasing time dependent backlogging rate; moreover variable holding cost and the effect of inflation are also taken into consideration. The model is illustrated with numerical experiments and convexity of the total average costs are revealed graphically, additionally sensitivity analyses with respect to the changes in system parameters are also discussed.