There can be three possibility for winning only one tender. Can win only a or only win b or only win c.

probability for winning a = 0.2.

probability of loosing a = 1 - 0.2 =0.8.

Similarly probability of loosing b and c are 0.7 and 0.6 respectively.

so probability of winning only one tender = win a * lose b * lose c + lose a* win b * lose c + lose a * lose b * lose c.

= 0.2 * 0.7 * 0.6+ 0.8 * 0.3 * 0.6 + 0.8 * 0.7 * 0.4


= .452 is the probability of getting only one tender.

Thank you.