clear
//
//
//

//Variable declaration    
h=6.6*10^-34;        //planck's constant(J-sec)
m=9.1*10^-31;    //mass of electron(kg)
lamda=0.4*10^-10;        //de-broglie wavelength(m)
e=1.6*10^-19;        //charge of electron(c)

//Calculations
V=h^2/(2*m*e*lamda^2);      //voltage(V)

//Result
printf("\n voltage is %0.1f V",V)
printf("\n answer in the book is wrong")