Concept:Multiply the negative characteristic and positive mantissa separately, then adjust the result to bar notation.Explanation:The number 2.7780 means −2+0.7780.Multiply by 5: 5×(−2)=−10, and 5×0.7780=3.8900.Sum: −10+3.8900=−6.1100.Express −6.1100 as a negative integer plus a positive mantissa between 0 and 1: −7+0.8900=−6.11.Thus the result is 7.8900.Answer:Option A: 7.8900