Table 1.

Parameters and their meanings.

Parameter	Meaning
$T_i$	$i^{th}$ (time) period
$s_j$	$j^{th}$ task site
$U_{T_i,s_j}$	the user set in the region $s_j$ during $T_i$
$R_{T_i,s_j}$(u)	the number of check-ins in the region of $s_j$ during $T_i$ for user u
$tas{k}_{T_i,s_j}$	the subtask in the region $s_j$ during $T_i$
$En$($U_{T_i,s_j}$)	the information entropy in the region $s_j$ during $T_i$
$hea{t}_{T_i,s_j}$	the heat of $s_j$ during $T_i$
$c_{T_i,s_j}$	the payment incentive coefficient of $tas{k}_{T_i,s_j}$