Economics help!?

Can someone help me with my econ homework? Under what cirstances to firms with access to the public bond market turn to issuance of bonds in the private market. Also, how will the convergence of the market price of a bond to par affect the relationship between the current yield and the yield to maturity and will it converge towar or depart fromt the coupon rate? Any help to any of these questions would be much appreciated!