Answer:
$0.30
Explanation:
We have been given that an advertiser who uses ad scheduling has a custom bid adjustment for 9 p.m. to 12 a.m. on weeknights. The normal bid is US$0.40 and the bid multiplier is -25%.
The advertiser bidding for the given time period would be $0.40 minus 25% of $0.40.
![\text{Advertiser bidding}=\$0.40-((25)/(100)\cdot \$0.40)](https://img.qammunity.org/2020/formulas/mathematics/high-school/40wnijqiqa08tgxjosi2dtkrdhcdsfwz93.png)
![\text{Advertiser bidding}=\$0.40-((1)/(4)\cdot \$0.40)](https://img.qammunity.org/2020/formulas/mathematics/high-school/1lpuj9vgmvuqi6mq22pz31o3guqwtmyffj.png)
![\text{Advertiser bidding}=\$0.40-((1)/(1)\cdot \$0.10)](https://img.qammunity.org/2020/formulas/mathematics/high-school/1srz9vhqttg133ch790j98kzluluq234zw.png)
![\text{Advertiser bidding}=\$0.40-\$0.10](https://img.qammunity.org/2020/formulas/mathematics/high-school/a80hor73y4caz746ic40xoihoy0lmq0cjv.png)
![\text{Advertiser bidding}=\$0.30](https://img.qammunity.org/2020/formulas/mathematics/high-school/8lcc44ag8qcqy2tx02z969laqolpo3hjc1.png)
Therefore, the advertiser bidding for 9 pm to 12 am would be $0.30.