Correct. The probability that one of the robots doesn’t finish in the top 4 spots is $\displaystyle\frac{{6}}{{10}}\usepackage{cmbright}\Huge\$ . Once that robot has taken a spot, the probability for the second robot is $\displaystyle\frac{{5}}{{9}}\usepackage{cmbright}\Huge\$ , and the third robot is $\displaystyle\frac{{4}}{{8}}\usepackage{cmbright}\Huge\$ . Multiply these probabilities to determine the probability that none of the robots finishes in the top four spots: $\displaystyle{\left(\frac{{6}}{{10}}\right)}{\left(\frac{{5}}{{9}}\right)}{\left(\frac{{4}}{{8}}\right)}=\frac{{120}}{{720}}=\frac{{1}}{{6}}\usepackage{cmbright}\Huge\$ .