Boral is a commercial shielding material consisting of approximately equal parts by weight of boron carbide (B4C) and aluminum compressed to about 95% theoretical density (2.608 g/cm3) and clad with thin sheets of aluminum 0.25 cm thick. The manufacturer specifies that there are 0.333 g of boron per cm2 of a boral sheet 0.457 cm in overall thickness. What is the probability that a 0.0253-e V neutron incident normally on such a sheet will succeed in penetrating it?