3. According to one cosmological theory, there were equal amounts of the two uranium isotopes

235U and 238U at the creation of the universe in the "big bang." At present there are 137.8 atoms

of 238U for each atom of 235U. Using the half-lives 4.468x109 years for 238U and 7.038x10³ years

for 235U, calculate the age of the universe.