After separating variables,and taking into account the facts given by the problem ,we integrate from 100 to p the fraction :

................... ....................

to get : .................................................. .............................1

Then we integrate ,kdt, from 1940 to 2009 and put k =1 and we get:

.............................69................... .............................................2

Now we equate (1) to (2) (1)=(2) we get:

................... =c.....................3

After doing calculations we have:

................... .................................................. ..........................4

And since c is very large we can substitute 1+c by c in 4 and thus finally have:

.....................................p=200 million........................................... .................................