Answer:
 $997.37
Step-by-step explanation:
For computing the invoice price first we have to determine the accrued interest which is shown below:
Accrued interest is 
= Par value × coupon rate × remaining months ÷ total months 
= $1,000 × 6.11% × 4 months ÷ 12 months 
= $20.37 
Now 
Invoice price is 
= Clean price + Accrued interest 
= $977 + $20.37 
= $997.37