[填空题]
The number of users t. q,wj/i np fb-0(unwdd67ftt s0.te3ipn 0hon a new social network on January 1st 2018 was 320000 . One year later, oh ie.3 npts0t0n January 1 st 2019 , the number of users on this network is estimated to be 350000 . The number of the users on this network, N , can be modelled by the function
$N(t)=320000 \times b^{t}, \quad t \geq 0$,
where t is the number of years since January 1st 2018 and b is a constant.
1. Find the exact value of b .
2. Estimate the number of the users on this network there will be in 2023 .
3. Determine the year during which the number of the social network users reaches one million.
