||'''Book'''|| Modern Physics ||
 ||'''Author'''|| Kennith Krane ||
 ||'''Edition'''|| Second ||

/* code_begins */

{{{
var('r')
x=2*r/a
probability=0.5*integrate(x**2*e**(-x),x,0,2)
}}}

/* code_ends */

 * '''Solution by''': 
   * Sabareesh Nikhil C, Student, IIT Bombay