function projectCost() public view override returns (uint256 _cost) {
    // Local instance of taskCount. To save gas.
    uint256 _length = taskCount;

    // Iterate over all tasks to sum their cost
    for (uint256 _taskID = 1; _taskID <= _length; _taskID++) {
        _cost += tasks[_taskID].cost;
    }
}
require(
    projectCost() >= uint256(_newTotalLent),
    "Project::value>required"
);
