[填空题]
The number of seats in an i.belu.a6 /z mauditorium follows n0(5 j veqqd8rlne,l-6ad +yf a regular pattern where the first row har6,aeqej 0n-fvl(5 dl8 nd+yqs $u_1$ seats, and the amount increases by the same amount, d, each row. In the fifth row, there are 62 seats and in the thirteenth row there are 86 seats.
1.Write down an equation, in terms of $u_1$ and d , for the amount of seats
1.1.in the fifth row.
$u_5$=$u_1$+ d
1.2.in the thirteenth row.
$u_{12}$=$u_1$+ d
2.Find the value of $u_1$ and d.
$u_1$= ; d= .
3.Calculate the total number of seats if the auditorium has 20 rows.
$S_{20}$= .
The cost of the ticket for a musical held at the auditorium is inversely proportional to the seat's row. The price for a seat in the first row is 120 dollars, and the price decreases 3% each row. Thus, the value of the ticket for seats in the second row is 116.40 and 112.91 in the third one, etc.
4.1.Find the price of the ticket for a seat in the fifth row, rounding your answer to two decimal places.
p5 = .
4.2.Find the row of the seat at which the price of a ticket first falls below 70.
n≈ .
4.3.Find the total revenue the auditorium generates by tickets sales if 40 seats in each of the 20 rows are sold. Give your answer rounded to the nearest dollar.
dollar= .
