This paper analyzes a monopolistic market maker's joint determination of quoted spreads and depths, as well as informed and uninformed traders' optimal submission strategies under various trading environments. The influence of quoted depths on traders' order-submission decisions is found to be significant. Therefore, the market maker can adjust quoted depths to avoid unfavorable trades on one side or both sides of the market. In addition, it is shown that traders are more willing to submit market orders when spreads decrease, depths increase, same-side limit order books are thicker, or expected future market order flows decrease. Conversely, limit orders are preferred.