21. Huixian's mother buys some shares of Company A on Day 0. On Day 7, the share price
of Company A is $4.60. If she sells all her shares
of Company A and buys 2000 shares of
Company B on Day 7, she would receive $7400.
On Day 12, the share price of Company A is
less than that on Day 7. If she sells all her shares
of Company A and buys 5000 shares of
$4.80 and the share price of Company B is $0.50
Company B on day 12, she would have to pay $5800.
Find
(1) the number of shares of Company A Huixian's
mother has,
(ii) the share price of Company B on Day 12.

An electronics manufacturer wants to know if customers would be interested in a detachable keyboard for their tables and if so, what the most important features would be. the manufacturer partners with an electronics store to include copies of the survey with every purchase at that store for one week. which of the following best explains why this random sample is unlikely to be a good representative sample of tablet owners' preferences for a detachable keyboard? a) one week is likely not enough time to get a large enough sample. b) most people won't bother to send in the survey, which is likely to skew the results c) there is no way to verify whether the responders to the survey actually own a tablet d) the survey is biased because it was conducted through an electronics store, not the general population

Which recursive formula can be used to determine the total amount of money earned in any year based on the amount earned in the previous year? f(n+1)=f(n)+5

For the rule of 78, for a 12-month period, the last term in the sequence is 12 and the series sums to 78. for an 10 month period, the last term is and the series sum is . for a 15 month period, the last term is and the series sum is . for a 20 month period, the last term is and the series sum is