Solution Let D_1D1 and D_2D2 be the event that athlete is disqualified previously and in next grading period, respectively.Given:P(D_2| D_1^c)= 0.15 ~~~~P(D_2|D_1)= 0.5 ~~~~P(D_1)=0.3P(D2∣D1c)=0.15 P(D2∣D1)=0.5 P(D1)=0.3Answer0.255