Change tk label text according to optionmenu

Question

Im making a program that will do most of my homework. In compound interest, it gives a different answer than should. 5=P. R=2. 1=T The answer when compounded quarterly shoul be 0.100 but it gives answer 0.9 .... And also i want the formula for compound interest to change according to the text in drop which is an optionmenu. Thecode---

canvas1.create_window(200, 470, window=entry12)
entry23 = Entry (root) 
canvas1.create_window(200, 530, window=entry23)
entry34 = Entry (root) 
canvas1.create_window(200, 590, window=entry34)

menu=StringVar()
menu.set("Compounded")
drop=OptionMenu(root, menu, "Compounded annually", "Compounded half yearly", "Compounded quarterly")
drop.config(bg="black", fg="white")
canvas1.create_window(200, 650, window=drop)

def getvalue2():
     p2=float(entry12.get())
     r2=float(entry23.get())
     t2=float(entry34.get())
     rr=r2/2
     tt=t2*2
     rrrr=r2/4
     tttt=t2*4
     if drop=="Compounded half yearly":
        duck=p2*(1+rr/100)**tt-p2
     elif drop=="Compounded quarterly":
        duck=p2*(1+rrrr/100)**tttt-p2
label=Label(root, text=float(duck))
solve=Button(text='Solve!', bg="red", command=getvalue2)
canvas1.create_window(200, 740, window=solve)```