<image>There is a helical spring scale, and when weighing items within 100 grams, the relationship between the item mass and the spring length is shown in the figure below:
(1) The original length of the spring is ____ cm.
(2) The spring extends by ____ cm when weighing a 70-gram object.
(3) When Xiaoming uses this spring scale to weigh a rock specimen, the spring length is 16 cm. How much does this rock specimen weigh?
