(*Comparison of the current yield and yield to maturity *)
A=6
T=30
P[y_]:=A*((1/y)-(1/(y((1+y)^T))))+ (100/((1+y)^T))
(* Convexity of Price and yield *)
Plot[ P[y],{y,.005,.20}, AxesLabel->{yield,P_B}]

(* Current yield *)
g[y_]:= A/P[y]

(* Relationship between current yield and yield; Note the current yield and yield to maturity are equal when the bond sells at par, indicated in red *)Plot[{g[y],y},{y,.005,.10}, Epilog-> {PointSize[Large],Red,Point[{.06,.06}]}, 
PlotLabel->{Current yield vs. y},
AxesLabel->{pct,{CY,y}}]
(* Plot of current yield *)
Plot[g[y],{y,.005,.10}, AxesLabel-> {pct,{CY}}]