Standard Costing

Could someone please provide me the answer for the following question?
Thanking you,

Standard Costing:
A company produces a product which has a standard variable production cost of $8 per unit made up as follows:
Direct Material $4.60 (2kg x $2.30 per kg)
Direct Labour $2.10 (0.7 hours x $3.00 per hour)
Variable overhead $1.30
Fixed manufacturing costs are treated as period costs.
The following information is available for the period just ended.
Variable manufacturing cost of sales (at standard cost) $263,520
Opening stock of finished goods (at standard cost) $120,800
Closing stock of finished goods (at standard cost) $146,080
Direct material price variance $2,571 unfavourable
Raw materials used in manufacture (at actual cost) $170,310
Direct labour rate variance $4,760
Direct labour efficiency variance $3,240 favourable

Required:
(a) Determine for the period just ended:
(i) The number of units produced
(ii) The raw material usage variance
(iii) The total actual direct labour cost, and
(iv) The actual cost per kg of raw material used.
(b) Outline the possible causes of the raw material variances.