Geometric sequences

In $2015$, $8688$ choir members sang in the largest gospel choir in Manila. Imagine, the conductor wrote an e-mail on January $1$st to three choir members. Each of them forwarded the e-mail to other three choir members on the next day and so on... On which day would all members receive the e-mail?

Candles are being lit at a commemoration in the square. Gradually, every $15$ seconds, two candles are lit from one already burning candle. It also took $15$ seconds to lit the first candle. After $4$ minutes, all candles were lit. How many candles were finally burning in the square?

A blouse is on sale and its price was reduced twice, each time by ten percent. The difference between its original and its final price is $133\mathrm{CZK}$. What was the blouse original price before the discounts?

The $n$th term of a geometric sequence is $3^{n-1}\cdot 2^{n+1}$. Find the second term and the common ratio.